It is common for vehicles, such as aircraft, that carry at least one gas turbine engine to include an environmental control system (ECS) for providing temperature conditioned, pressurized air to the pilot, passengers, and heat generating electronics; an auxiliary power unit (APU) to supply auxiliary power for the aircraft; and an emergency power unit (EPU) to provide emergency power from a self-contained fuel and/or oxidizer supply commonly known as a stored energy system (SES), which, typically, is insensitive to altitude and can be activated quickly for rapid starting of the EPU.
Typically, the APU, EPU and ECS are turbo machines. There is a continuing desire to integrate the functions of these various systems into a single turbo machine to reduce components and weight. However, some prior attempts to integrate these various systems have created unacceptable performance penalties, such as unacceptable rates of fuel usage, because the optimum turbo machines of each of the various functions are of different size, speed and configuration.